text: Using just a few parts per million of the drag reducer helps to reduce the turbulence inside the pipe. Because the oil pushes up against the inside wall of the pipe, the pipe pushes the oil back down causing a swirling of turbulence to occur which creates a drag force. When the polymer is added, it interacts with the oil and the wall to help reduce the contact of the oil with the wall.
  Degradation can occur on the polymers during the flow. Because of the pressure and temperature on the polymers, it is easier to break them down. Because of this, the drag reducing agent is re-injected after points like pumps and turns, where the pressure and temperature can be extra high. To safeguard against degradation at high temperature, a different class of drag reducing agents are at times used, namely, surfactants. Surfactant is a very convenient contraction of the term Surface-active agent.  It connotes an organic molecule or an unformulated compound having surface-active properties.  All three classes of surfactants, namely, anionic, cationic and nonionic surfactants, have been successfully tried as drag-reducing agents.
  Knowing what will create the ideal drag reducer is key in this process. Ideal molecules have a high molecular weight, shear degradation resistance, are quick to dissolve in whatever is in the pipe, and have low degradation in heat, light, chemicals, and biological areas.
  With drag reduction, there are many factors which play a role in how well the drag is reduced. A main factor in this is temperature. With a higher temperature, the drag reducing agent is easier to degrade. At a low temperature the drag reducing agent will tend to cluster together. This problem can be solved easier than degradation though, by adding another chemical, such as aluminum to help lower the drag reducing agent's inter-molecular attraction.
  Other factors are the pipe diameter, inside roughness, and pressure. Drag is higher in smaller diameter pipe. The rougher the inside surface of the pipe, the higher the drag, or friction, which is measured by the Reynold's number. Increasing the pressure will increase flow and reduce drag, but is limited by the maximum pressure rating of the pipe.